This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A155640 #25 Jul 26 2024 10:21:21
%S A155640 1,3,25,219,1777,13683,102025,745419,5374177,38400483,272709625,
%T A155640 1928498619,13597146577,95668307283,672119557225,4717043931819,
%U A155640 33080342678977,231867574534083,1624598900644825,11379821699045019,79696898865971377,558069026925080883
%N A155640 a(n) = 7^n - 5^n + 1^n.
%H A155640 Paolo Xausa, <a href="/A155640/b155640.txt">Table of n, a(n) for n = 0..1000</a>
%H A155640 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (13,-47,35).
%F A155640 G.f.: 1/(1-7*x)-1/(1-5*x)+1/(1-x).
%F A155640 E.g.f.: e^(7*x)-e^(5*x)+e^x.
%F A155640 a(n) = 12*a(n-1)-35*a(n-2)+24 with a(0)=1, a(1)=3. - _Vincenzo Librandi_, Jul 21 2010
%t A155640 Table[7^n - 5^n + 1, {n, 0, 25}] (* _Paolo Xausa_, Jul 26 2024 *)
%o A155640 (PARI) a(n)=7^n-5^n+1 \\ _Charles R Greathouse IV_, Sep 24 2015
%Y A155640 Cf. A155624, A155625, A155626, A155627, A155628, A155629, A155630, A155631, A155632, A155633, A155634, A155635, A155636, A155637, A155638, A155639.
%K A155640 nonn,easy
%O A155640 0,2
%A A155640 _Mohammad K. Azarian_, Jan 30 2009